Implementation of real-time MPEG-4 FGS encoder

Yen Kuang Chen, Wen-Hsiao Peng

研究成果: Conference contribution同行評審


While computers become faster than they used to be, software implementation of the latest video codec in real time is still a challenging topic. This paper presents our techniques in optimizing the speed of MPEG-4 Fine Granularity Scalability (FGS) video encoders. First, zigzag scans are slow processes in video encoding and decoding. While state-of-the-art processors utilize hardware data prefetchers to reduce memory latency, non-sequential addresses in the zigzag scan may destroy the trackability of hardware prefetching. The problem is even more serious in MPEG-4 FGS where we need multiple scans in bit-plane coding. More than 30% of CPU time is for bit-plane encoding in an MPEG-4 FGS encoder (including base layer and enhancement layer). In this work, we rearrange the layout of the image structure so that zigzag scans are in sequential memory locations. After the rearrangement, there are prefetch reads and we see 80% speed-up in bit-plane encoding. Second, variable length encoder (VLC) incurs a huge number of unpredictable conditional branches. While modern processors can execute tens of instructions in their pipeline, a mis-predicted branch will decrease the efficiency of the pipeline. The problem is severer in MPEG-4 FGS where we need multiple bitplane VLC’s. More than half of the CPU time for MPEG-4 FGS enhancement layer encoder is on bit-plane VLC’s. In this work, we also design a bit-plane VLC algorithm, which has fewer unpredictable branches. The new design reduces mis-predicted branches by 2.4x. After these changes, overall speed-up in our MPEG-4 FGS software encoder is 1.4x without any assembly and MMX technology optimization.

主出版物標題Advances in Multimedia Information Processing - PCM 2002 - 3rd IEEE Pacific Rim Conference on Multimedia, Proceedings
編輯Yung-Chang Chen, Long-Wen Chang, Chiou-Ting Hsu
發行者Springer Verlag
ISBN(列印)3540002626, 9783540002628
出版狀態Published - 2002
事件3rd IEEE Pacific Rim Conference on Multimedia, PCM 2002 - Hsinchu, Taiwan
持續時間: 16 12月 200218 12月 2002


名字Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)


Conference3rd IEEE Pacific Rim Conference on Multimedia, PCM 2002


深入研究「Implementation of real-time MPEG-4 FGS encoder」主題。共同形成了獨特的指紋。